I will be updating this thread as info is given to me about this issue. Feel free to chime in if you like with thoughts.

I dropped her off yesterday morning and tried to explain all that was going on with her recently. I made this appointment last week when I was noticing that there was a flare in the shifting in Sport mode between 2-3 and 3-4. Well on Wednesday of last week, on my way into work (about 4 miles away) just as I was leaving the driveway all hell breaks loose as I start driving away. The dash is lit up all over the place. Check engine warning and chime, ABS failure warning light/symbol and chime, big red X call dealer warning and chime, the speedo is bouncing all over the place and the car is now in limp mode (stuck in 2nd gear). I need to get to work so off I go.

I try not to run her above 3K RPM as it just feels bad and the local speed limit of 35 needed to be watched. I don't even know what speed I am going because the speedo is bouncing all around. I drive her home and leave for Thanksgiving and don't drive her again until driving her yesterday to the dealer.

I have a OBDII reader and got a U0073 code I think(this is from memory now) and there was still the check engine light but the car shifted thru all gears. I got it to do the flare for the tech as well as the shudder at 48MPH. It is at the dealer and the thought so far is obviously transmission, but they are not sure where the issue is and if a repair can be made or a new one in installed. I vote for the new one. I really don't want to deal with this again in a few months, and feel any repair will lead to that.

If that code # you posted from memory turns out to be correct, my read is, that you lost a whole bunch of communication (high and or low speed GMLAN), between some of the various computer modules throughout the car. If I read your post properly, to me it sounded like some of the total list of problems has disappeared, on your drive to the dealer. Maybe it will turn out to be as simple as down powering the car for a shot period of time. Powering up, an getting the *welcome* display in the DIC. Minus the transmission flare you talked about.
It looks like the BCM is the main cog in this comm data circuit. So *it* might be the most suspected item here. I'll be looking for your follow-on posts for the solution they find and to learn some stuff from you at the same time.

I am not sure if this is the issue, but I remember reading on hear a while back a very similar issue. It turned out to be the TCU was bad. If I remember right the TCU is inside the transmission and it was easier for them to replace the whole transmission. This is going off deshavu from a while back, so I am not 100% sure on the accuracy.

Well after 2 days the tech still isn't sure of the source of the noise and vibration. This is just a touch frustrating. I'd like to know what the issue is but I need to give them a little more time. What I do know is that all the noises and vibrations that I have been feeling, the tech and shop foreman have been feeling too, so I am happy about that. They have ruled out AFM for causing the rumble strip vibration. They will be replacing the motor mounts that there is a TSB for to help with that vibration. They are also looking into the prop shaft/driveshaft as the source. Not sure though. There are many codes the car is throwing right now. Many dealing with the transmission. This isn't going to be completed anytime soon as the shop foreman was explaining he needs a bunch more info and will need to talk to an engineer at GMC in order to get a prop shaft released for the car if that in fact is the issue.

In the meanwhile I have a rental, a white cargo van, LOL. Like only 2 seats in it no side windows that I am tooling around in. Think I will bring in my 33"wide Troy built mower for servicing while I have the van for ease of transporting, and not dirty my Expedition. Something good is coming out of this after all. While they have her they will be mounting 2 new tires up front and two rims and tires I bought a while back on this site on the rears. I just did the front brake pads and rotors myself, and bled the brakes as well. She will be like new soon enough, I hope.

What has been figured out is that the vibration at the 47-48 MPH speed was from the torque converter and a new one is going to be installed. I'll take it.
They are going to install new motor mounts to reduce the engine vibration that is detectable when the car is in AFM. I'll take that too.
Next up is the transmission. As per engineers at GMC, they want it out and taken apart. That will happen tomorrow. I'd really like a new updated transmission there too. Fingers are crossed on this one.

So far all is covered under the power-train warranty on the car. Psyched about that. Gotta love it when a car manufacturer/dealer is taking care of you. So far.

OK so here it is, the DIAGNOSIS!! I'm not really happy about it, and I am really irritated with myself, but it is what it is.

I got a call from the shop foreman on Friday afternoon to hear where we are with the car. After he dropped the pan, what he saw was water in the transmission oil. Humph, that's not good at all. How did water get there is the $3500 repair question for the new transmission and torque converter that is needed, as well as complete flush. He had a very simple explanation. He was also very certain that it was NOT coolant from the radiator cooler. That would be a frosty color which it was not.

On my G8 he noticed my transmission dipstick tube that I installed a while back. Almost 2 years ago or so. He is seeing that it is not sealed where it goes into the transmission. I remember seeing it having a rubber O ring on the bottom of the tube when I installed it, but hindsight is always 20/20, that little O ring isn't going to seal out much of anything. For the past almost two years, every time it has rained, it has hit the tube under the car as spray, run down the tube, and slowly leaked into the transmission, where water is a very bad thing.

What I have been doing everytime or so when I change the engine oil is to open the transmission plug, drain out about 2 quarts of transmission fluid, (measuring it so I would know how much to put back in) and then re-add the equal amount of Dextron VI down the transmission tube, it couldn't get much easier. The thought is to maintain this car as I love it and want it to last for quite a long time. What has been really happeneing is that I was slowly killing the transmission.

TAKE HOME POINT--------------IF YOU ARE USING THIS TYPE OF DIPSTICK TUBE, CANADIANEH WAS SELLING THEM, PLEASE DO YOURSELF A FAVOR. CHECK THE SEALING OF THE TUBE INTO THE TRANSMISSION AND ADD SOME SILICONE OR SOMETHING TO PREVENT WATER FROM LEAKING IN.

From here on out, I am going to be doing what the manual says. Every 50k or so, drop the pan, change the filter and re-add to the correct level.
Please also everyone here understand, I am not calling out anyone I am really just trying to help out fellow members not have the same issue I have and save some serious expense.

quite a turn of events indeed. The dealer is going to help me out substantially for the cost. They are calling it "good will" as they consider me a valued customer. I am hoping to get her back later this week. We will see.

Quote:

Originally Posted by zepcom

Whoa, such a turn of events.

So you're liable for the repair on this since the dealership deemed "the aftermarket modification caused the water damage" ?

Hmmmm.... caviat emptor!

I'm glad that I never fell for the "equip your car with a tranny dipstick" coolaid, yikes!

I had problems with mine sealing, they sent me a new a new dipstick but I never installed it and mine is still sealed as it was from the factory. The dip stick just didn't fit properly, so I didn't want to take any chances. Good luck and sorry to hear about your ordeal and glad to hear the dealer is willing to help you out a little with the cost. See there are still some good people left.

I appreciate the thoughts guys. They Fed Exed the trans to the dealer and should have gotten it today. It's too late to call now. maybe tomorrow she will be done, most likely on Thursday. It'll be nice to get her back home.

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